IP3R drives cardiomyocyte injury by enhancing MAM-mediated Ca²⁺ transfer and mitochondrial dysfunction

Heart failure (HF) is the terminal stage of various cardiovascular diseases. Mitochondrial Ca²⁺ overload and dysfunction mediated by mitochondria-associated ER membranes (MAMs) are recognized contributors to HF pathogenesis; however, the underlying molecular mechanisms remain incompletely understood.

An in vitro model of cardiomyocyte injury was established using angiotensin II (Ang II)-stimulated H9c2 cells. IP3R was knocked down using specific siRNA. Cell viability (CCK-8), apoptosis (Annexin V/TUNEL), and hypertrophy (phalloidin staining) were assessed. IP3R expression and mitochondrial complex subunits were analyzed by western blotting. MAM formation was examined by transmission electron microscopy and immunofluorescence co-localization. Mitochondrial function was evaluated by measuring ATP levels, ROS (MitoSOX), mitochondrial membrane potential (TMRM), and Ca²⁺ uptake (Rhod-2).

Ang II stimulation reduced cell viability, induced hypertrophy and apoptosis, and promoted MAM formation. Mechanistically, Ang II upregulated IP3R expression and enhanced MAM-mediated mitochondrial Ca²⁺ overload, leading to decreased mitochondrial membrane potential, elevated ROS, and reduced ATP production. Notably, genetic knockdown of IP3R attenuated these pathological changes, reducing MAM formation and mitochondrial Ca²⁺ overload while restoring mitochondrial function and cell viability.

Our findings suggest that IP3R may exacerbate cardiomyocyte injury by facilitating MAM-mediated Ca²⁺ transfer and mitochondrial dysfunction, indicating that targeting IP3R could represent a potential therapeutic strategy for HF. However, the upstream mechanisms of IP3R upregulation and the causal role of mitochondrial Ca²⁺ uptake require further investigation.